1. Field of the Invention
This invention relates to the production of laminated glazings and in particular a device for the assembly of constituent elements of a laminated glazing by pressing, in particular by calendering, i.e., by pressing of the stack of said constituent elements, designated as glazings in the following description, between upper pressing means and lower pressing means.
2. Description of the Related Art
The known calendering devices, described for example in the publication of French patent 2 053 104, are generally equipped with two series of pressing rollers: a series of lower rollers placed beside one another, their position being adjusted independently so as to obtain a curvature corresponding to the desired crosswise curvature which is generally the mean curvature of the glazing, and a series of upper rollers placed approximately in the same way. In the known devices, the two series of rollers are each mounted on a crosswise beam belonging to a frame that can pivot around a horizontal pin, the whole constituting a mobile unit, so that the rollers remain approximately perpendicular to the glazing during the entire assembly operation.
During the passage of the glazing between the rollers, the position of these rollers must vary to follow the changes in the crosswise curvature of the glazing. For this purpose, a calender has already been proposed in the publication of European patent EP 0 189 345 that uses pneumatic cylinders that obtain a great flexibility for the rollers in following the curvature of the glazing. In this calender, of the type known as "floating," the compression chambers of the cylinders of the upper rollers and those of the cylinders of the lower rollers ar in communication and the pneumatic pressure being exerted on a pressure roller is equal to that being exerted on a counterpressure roller.
These devices are generally suited for the assembly of glazings exhibiting a crosswise bending that is smooth and not very accentuated and when this crosswise bending of the glazing is approximately the same over the entire length of the glazing. But for glazings having more complex shapes, particularly for glazings that exhibit a bending that is very deep in the crosswise section and/or irregular over the length of the glazing, these known devices are not always satisfactory because they are not flexible enough to be able to follow all the significant changes in curvature. If the pressure of the rollers is too low, an insufficient or not very homogeneous adhesion of the constituent elements of the glazings results and if the pressure is too great, breaks in the glazing result.
To increase the flexibility of the device, the applicant attempted using rollers of small width and increasing their number. But this causes the problem of increased bulk of the series of pneumatic cylinders placed beside one another in the vertical plane passing through the pressing line.